Allow configuration to disable the International state ("Strict negotiation")

Problem/Motivation

The "International" state is when a language prefix is supplied but not a country prefix (e.g. /en/).

Support for this is hard-coded presently, but some use cases require it not to be disabled.

Proposed resolution

Suggest completely removing support for this from this module. If the user wishes to support this scenario, they can enable core's Language from the URL (Path prefix or domain) negotiation method.

This may require LCM to stop piggy-backing on that method's prefix configuration. See ✨ Allow configuration options for the prefix pattern Active .